The present invention relates to a circuit board/printed circuit board having pre-reserved conductive heating circuits and, more particularly, to a multi-layer circuit board/printed circuit, wherein a metal substrate having pre-reserved conductive heating circuit can generate heat quickly, directly and uniformly at the demanded position to get high quality of bonding strength and hardening.
FIGS. 1 and 1A show the conventional manufacturing way of pre-stacked multi-layer metal circuit boards by rivet, wherein a plurality of metal circuit substrates 10a and a plurality of layers of insulating material 11a are pre-stacked and riveted and positioned with rivets 20a. In addition to wasting the cost of rivets, there are some problems of rivet in this conventional way. If the thickness of rivet is not thick enough, the mechanical intensity is quiet weak and it is easy to be deformed in riveting and pressing process. If the thickness of rivet is too thick, it is hard to rivet and clap board tightly. The other problem is that the finished height of riveted rivet is over the height of pre-stacked multiplayer metal circuit board. Owing to this little height difference, the area of pre-stacked multiplayer board near riveted rivets cannot get sufficiently direct pressure and heat to laminate in the lamination process. After this process, there are many of voids inside the board. These defects will affect the performance of board like electricity, thermal reliability and insulation. Moreover, in the size and dimension, the rivet""s main body 20b is different each to each. This condition will make alignment of layer to layer run way.
FIGS. 2 and 2A show the conventional manufacturing way of pre-stacked multi-layer metal circuit boards by indirect heating, wherein a plurality of circuit substrates 10a and a plurality of layers of insulating material 11a (e.g., resin) are pressed and heated with hot bar 30a to make them bond together. While this indirect heating way is applied to metal circuit board of more layers, there is large variation of temperature gradient from touched pot of hot bar to middle of pre-stacked more layer board. The outside is high temperature, but the inside is low temperature.
Temperature gradient makes each insulating material 11a in this pre-stacked multi-layer circuit board have different viscosity and degree of bond and hardening. This different viscosity makes layers shift. Whether the heater""s temperature and heating time are enough or not will cause difference of degree of bond and hardening. If the temperature of hot bar or bonding time is increased, the inside layer may have a better degree of bond, but the outside layers have been burnt and stripped off. These conditions will greatly affect quality and mechanical strength.
Accordingly, the above conventional pre-stacked multi-layer metal circuit boards have inconvenience and drawbacks in practical use. The present invention aims to resolve the problems in the prior art.
The primary object of the present invention is to provide a circuit board/printed circuit board having pre-reserved conductive heating circuits, wherein electricity is provided to each layer via a power supply system to heat each layer fast. The time of bond is short, the heat of each layer is uniform, direct and easily controllable, and consumables such as rivets and hot bar are not required. Moreover, the number of heating regions can be increased unlimitedly according to necessity. No matter what the number of layers is, each layer can be heated simultaneously to bond and harden at the same short time, and the bonding strength and hardening is high and uniform. The cost can also be effectively reduced much.
To achieve the above object, the present invention provides a circuit board/printed circuit board having pre-reserved conductive heating circuits, which comprises a plurality of metal circuit substrates and a plurality of layers of insulating material. The conductive heating circuits are pre-reserved at the sides of the metal circuit substrates. The conductive heating circuits are disposed at the regions where the insulating material is to be bonded and sealed. Each of the conductive heating circuits has a plurality of direct heat-generating regions. The insulating material is disposed between the metal circuit substrates. When a power supply system provides currents to the conductive heating circuits, heat required for partly sealing can be generated so that the insulating material and the corresponding positions of the direct heat-generating regions on the metal circuit substrates can be bonded together and hardened.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which: